<!DOCTYPE html>
<html>
<head>

<meta name="viewport" content="width=800">
<style>
html { font-size: 16px; }
body { width: 800px; margin: 0; overflow-y: hidden; }
</style>

</head>
<body>

<div style="font-size: 2.5rem">
    This text should be autosized to 40px computed font-size, since although this has a narrow child block, the cluster will still be wide and need autosizing.
    <div style="width: 600px">
        This text should be autosized to 40px computed font-size as it is a part of the same cluster as the parent div.<br>
        Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
    </div>
    This text should be autosized to 40px computed font-size, similarly to the text at the top.<br>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
</div>

</body>
</html>